Barrantes Francisco J
Laboratory of Molecular Neurobiology, Institute of Biomedical Research, Faculty of Medical Sciences, Pontifical Catholic University of Argentina-National Scientific and Technical Research Council Buenos Aires, Argentina.
Front Synaptic Neurosci. 2014 Nov 4;6:25. doi: 10.3389/fnsyn.2014.00025. eCollection 2014.
Synapse efficacy heavily relies on the number of neurotransmitter receptors available at a given time. In addition to the equilibrium between the biosynthetic production, exocytic delivery and recycling of receptors on the one hand, and the endocytic internalization on the other, lateral diffusion and clustering of receptors at the cell membrane play key roles in determining the amount of active receptors at the synapse. Mobile receptors traffic between reservoir compartments and the synapse by thermally driven Brownian motion, and become immobilized at the peri-synaptic region or the synapse by: (a) clustering mediated by homotropic inter-molecular receptor-receptor associations; (b) heterotropic associations with non-receptor scaffolding proteins or the subjacent cytoskeletal meshwork, leading to diffusional "trapping," and (c) protein-lipid interactions, particularly with the neutral lipid cholesterol. This review assesses the contribution of some of these mechanisms to the supramolecular organization and dynamics of the paradigm neurotransmitter receptor of muscle and neuronal cells -the nicotinic acetylcholine receptor (nAChR). Currently available information stemming from various complementary biophysical techniques commonly used to interrogate the dynamics of cell-surface components is critically discussed. The translational mobility of nAChRs at the cell surface differs between muscle and neuronal receptors in terms of diffusion coefficients and residence intervals at the synapse, which cover an ample range of time regimes. A peculiar feature of brain α7 nAChR is its ability to spend much of its time confined peri-synaptically, vicinal to glutamatergic (excitatory) and GABAergic (inhibitory) synapses. An important function of the α7 nAChR may thus be visiting the territories of other neurotransmitter receptors, differentially regulating the dynamic equilibrium between excitation and inhibition, depending on its residence time in each domain.
突触效能在很大程度上依赖于特定时间可用的神经递质受体数量。一方面,受体的生物合成、胞吐释放和循环利用与另一方面的胞吞内化之间的平衡,除此之外,细胞膜上受体的横向扩散和聚集在决定突触处活性受体的数量方面起着关键作用。移动受体通过热驱动的布朗运动在储存区室和突触之间运输,并通过以下方式在突触周区域或突触处固定:(a) 由同型分子间受体 - 受体缔合介导的聚集;(b) 与非受体支架蛋白或下方细胞骨架网络的异型缔合,导致扩散“捕获”,以及 (c) 蛋白质 - 脂质相互作用,特别是与中性脂质胆固醇的相互作用。本综述评估了其中一些机制对肌肉和神经元细胞的典型神经递质受体——烟碱型乙酰胆碱受体(nAChR)的超分子组织和动力学的贡献。对目前来自各种通常用于研究细胞表面成分动力学的互补生物物理技术的可用信息进行了批判性讨论。nAChR 在细胞表面的平移流动性在肌肉和神经元受体之间在扩散系数和在突触处的停留时间方面有所不同,其覆盖了广泛的时间范围。脑α7 nAChR的一个独特特征是它能够在突触周区域花费大量时间,紧邻谷氨酸能(兴奋性)和γ-氨基丁酸能(抑制性)突触。因此,α7 nAChR的一个重要功能可能是访问其他神经递质受体的区域,根据其在每个区域的停留时间,差异性地调节兴奋与抑制之间的动态平衡。